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Table 45. Layer 2 Overhead
Layer 2 Overhead Difference Between Link MTU and IP MTU
Ethernet (untagged) 18 bytes
VLAN Tag 22 bytes
Untagged Packet with VLAN-Stack Header 22 bytes
Tagged Packet with VLAN-Stack Header 26 bytes
Link MTU and IP MTU considerations for port channels and VLANs are as follows.
Port Channels:
All members must have the same link MTU value and the same IP MTU value.
The port channel link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the
channel members.
For example, if the members have a link MTU of 2100 and an IP MTU 2000, the port channels MTU values cannot be higher
than 2100 for link MTU or 2000 bytes for IP MTU.
VLANs:
All members of a VLAN must have the same IP MTU value.
Members can have different Link MTU values. Tagged members must have a link MTU 4bytes higher than untagged
members to account for the packet tag.
The VLAN link MTU and IP MTU must be less than or equal to the link MTU and IP MTU values configured on the VLAN
members.
For example, the VLAN contains tagged members with Link MTU of 1522 and IP MTU of 1500 and untagged members with Link
MTU of 1518 and IP MTU of 1500. The VLANs Link MTU cannot be higher than 1518 bytes and its IP MTU cannot be higher
than 1500 bytes.
NOTE:
When configuring IP MTU on an interface, make sure to set the same or maximum IP MTU value on both ingress
and egress interfaces to make IPv4 traffic flow.
Configuring wavelength for 10Gigabit SFP+ optics
You can set the wavelength for tunable 10Gigabit SFP+ optics using the wavelength command. To set the wavelength,
follow these steps:
Enter the interface mode and set the wavelength.
INTERFACE mode
wavelength 1529.0
The wavelength range is from 1528.3 nm to 1568.77nm.
Verify configuration changes.
INTERFACE mode
show config
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Interfaces